/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.ide.jseditor.client.reconciler;

import org.eclipse.che.ide.api.text.TypedRegion;

/** A dirty region describes a document range which has been changed. */
public class DirtyRegion implements TypedRegion {

    /** Identifies an insert operation. */
    final static public String INSERT = "__insert"; //$NON-NLS-1$

    /** Identifies a remove operation. */
    final static public String REMOVE = "__remove"; //$NON-NLS-1$

    /** The region's offset. */
    private int fOffset;

    /** The region's length. */
    private int fLength;

    /** Indicates the type of the applied change. */
    private String fType;

    /** The text which has been inserted. */
    private String fText;

    /**
     * Creates a new dirty region.
     * 
     * @param offset the offset within the document where the change occurred
     * @param length the length of the text within the document that changed
     * @param type the type of change that this region represents: {@link #INSERT} {@link #REMOVE}
     * @param text the substitution text
     */
    public DirtyRegion(int offset, int length, String type, String text) {
        fOffset = offset;
        fLength = length;
        fType = normalizeTypeValue(type);
        fText = text;
    }

    /**
     * Computes the normalized type value to ensure that the implementation can use object identity rather than equality.
     * 
     * @param type the type value
     * @return the normalized type value or <code>null</code>
     * @since 3.1
     */
    private String normalizeTypeValue(String type) {
        if (INSERT.equals(type))
            return INSERT;
        if (REMOVE.equals(type))
            return REMOVE;
        return null;
    }

    /*
     * @see ITypedRegion#getOffset()
     */
    public int getOffset() {
        return fOffset;
    }

    /*
     * @see ITypedRegion#getLength()
     */
    public int getLength() {
        return fLength;
    }

    /*
     * @see ITypedRegion#getType
     */
    public String getType() {
        return fType;
    }

    /**
     * Returns the text that changed as part of the region change.
     * 
     * @return the changed text
     */
    public String getText() {
        return fText;
    }

    /**
     * Modify the receiver so that it encompasses the region specified by the dirty region.
     * 
     * @param dr the dirty region with which to merge
     */
    void mergeWith(DirtyRegion dr) {
        int start = Math.min(fOffset, dr.fOffset);
        int end = Math.max(fOffset + fLength, dr.fOffset + dr.fLength);
        fOffset = start;
        fLength = end - start;
        fText = (dr.fText == null ? fText : (fText == null) ? dr.fText : fText + dr.fText);
    }
}
